Dental filling material

ABSTRACT

A dental filling material comprising an inner core and outer layer of material disposed and surrounding the inner core, both the inner core and outer layer of material each containing a thermoplastic polymer. The thermoplastic polymer may be biodegradable. A bioactive substance may also be included in the filling material. The thermoplastic polymer acts as a matrix for the bioactive substance. The composition may include other polymeric resins, fillers, plasticizers and other additives typically used in dental materials. The filling material is used for the filing of root canals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.10/914,057, filed Aug. 6, 2004, which is continuation-in-part ofapplication Ser. No. 10/465,416, filed Jun. 18, 2003, which is acontinuation-in-part of application Ser. No. 10/304,371, filed Nov. 26,2002, which is a continuation-in-part of application Ser. No. 10/279,609filed Oct. 24, 2002, which claims priority to provisional ApplicationSer. No. 60/336,500 filed Oct. 24, 2001.

FIELD OF THE INVENTION

This invention relates to filling materials for use in filling dentalcavities and for root canal treatments.

BACKGROUND OF THE INVENTION

Endodontics or root canal therapy is that branch of dentistry that dealswith the diseases of the dental pulp and associated tissues. One aspectof endodontics comprises the treatment of infected root canals, theremoval of diseased pulp tissues, followed by the biomechanicalmodification and the subsequent filling of the pulp cavity (root canal).Root canal therapy is generally indicated for teeth having soundexternal structures but having diseased, dead or dying pulp tissues.Such teeth may or may not generally possess intact enamel and dentin andare satisfactorily engaged with bony tissue. In such teeth, the pulptissue and excised portions of the root should be replaced by abiocompatible substitute. One technique for the preparation of a rootcanal involves creating a coronal access opening with a conventionaldental drill. A tool is used for gross removal of pulp material from theroot canal through the coronal access opening. The void formed isenlarged with reamers and/or files to result in a fully excavatedcavity. Debris is removed from this cavity by flushing and the cavity iscleansed to remove all diseased tissue. This process, while essential,results in a root canal that is weakened and susceptible to fracture.Following chemical antisepsis, the excavated canal is ready for filling.

A basic method involves inserting a filling cone into a root canal andcementing therein to obturate the canal. The common root canal fillingcone material is made from gutta-percha. Lateral condensation is amethod in which several filling cones, a primary cone and auxiliarycones, are inserted into a root canal. The primary cone is inserted andcemented to the seat of the root canal. Using a tapered spreader, theprimary cone is then squeezed against the side of the root canal and asecond cone is inserted and cemented into place. This process iscontinued until the root canal is completely obturated which can requireup to 10 to 15 filling cones. Vertical condensation of warm or hotgutta-percha is yet another method of sealing root canals. Aftercementing a primary cone short of the apex of the root canal, heatapplication is alternated with a series of smaller and smaller pluggersuntil the gutta-percha is moved to the apex. This is often possible whenthe smallest plugger approaches the apex of the tooth within 3 to 5millimeters. The space is then backfilled. Lateral canals are packed andsealed as a consequence of lateral expansion of a wave of heatedgutta-percha. Alternatively, small segments of gutta-percha can be usedin this method that are inserted into the root canal, heated in orderthat they can adhere to one another and each backfilled one at a timeuntil the root canal is filled. All three of these methods, the singlefilling cone, lateral condensation and vertical condensation apply rootcanal cement or sealer around the individual cones or in betweensegments as a binding agent.

Another method employs an injection gun that injects warm or hotgutta-percha filling material into a root canal. The injector initiallyplaces heated gutta-percha at the apical area of the root canal througha needle-like canula tip and fills the gutta-percha into any surroundingvoids/spaces under pressure or at the seat of the root canal which isthen condensed with a plugger into the root tip. The injector thenbackfills the root canal by injecting additional gutta-percha into theroot canal until it is obturated. A similar method involves heatinggutta-percha on a flexible metal or plastic carrier used to insert thegutta-percha into the root canal. The carrier may be a solid rod, or ahollow rod, situated in the center of a master cone. The rod isconnected to a handle which may be removed by slipping it out of thehollow rod, or cutting it off if it is a solid rod.

Most of the current methods employed in obturating a canal use agutta-percha material that is inert in nature and will not be absorbedor degraded by the living tissue if the root canal is overfilled andextends beyond the apex. It has been a challenge for dentists to controlthe exact amount of the material within the border of the root canal toavoid overfilling. The cold core of gutta-percha is not malleable sothat it cannot be molded to the canal walls, resulting in pooradherence. In addition, when heated gutta-percha cools to bodytemperature in the root, a uniform contraction takes place furtherreducing adherence to the walls of the canal. Moreover, gutta-perchamaterial is a polyisoprene rubber material in nature, which does nothave the capability to bond to most dental materials, especially whenthe root canal sealer is a polymer-based material. Due to poor adherenceand bonding, existing bacteria in the root canal can multiply or leakagemay result, causing bacteria to enter the canal from the mouth, whichcan lead to the persistence of an infection or other complications.Gutta-percha exhibits poor strength and brittleness. Dental gutta-perchapoints/cones tend to break in harsh conditions, e.g., sharply curvedroot canals, tight spaces during a root canal treatment, and the like.

It is desirable to provide a root canal filling material that bondseasily to sealants. It is preferable that the root canal fillingmaterial have proper strength and flexibility. It would be advantageousif the root canal filling material could be retrievable or dissolvable.It would be highly advantageous if the root canal filling material couldreduce or eliminate bacterial leakage. It would be beneficial if thecavity filling material and root canal filling material could bebioactive. It would be further advantageous if the root filling materialstrengthened the root. It would be beneficial if the root fillingmaterial could be softened without effecting the overall strength andintegrity of the filling material.

SUMMARY OF THE INVENTION

These and other objects and advantages are accomplished by the fillingmaterial of the present invention comprising a thermoplastic polymer.The thermoplastic polymer is preferably a biodegradable polymer. Abioactive substance may be combined with the biodegradable thermoplasticpolymer. The thermoplastic polymer acts as a matrix for the bioactivesubstance. The composition may include other polymeric resins, fillers,plasticizers and other additives typically used in dental fillermaterials.

In one embodiment herein, the filling material is used for the fillingof dental cavities or root canals. The material may be placed in a rootcanal that has been opened to a predetermined dimension by use ofendodontic files, to seal the apical end. If necessary, the fillingmaterial can be compacted toward the apex, while it is still in thesoftened state, to ensure the apex is adequately sealed. If, by chance,the filling material is pushed slightly past the apex, or seeps throughthe apex, or comes in contact with fluids in the mouth, thebiodegradable material will disintegrate or break down and be absorbedor partially absorbed by the surrounding living tissues. If a bioactivesubstance is present in the filling material, it will react with thetissue in the mouth, mending and/or growing tissue to fill in any gapsor openings.

In another embodiment herein, the filling material includes an innercore section and outer layer of material disposed on and surrounding theinner core section. The inner core section and the outer layer ofmaterial are each fabricated of a thermoplastic polymer matrix.

The thermoplastic polymer matrix in the inner core section has a meltflow index that is lower than the melt flow index of the thermoplasticpolymer in the outer layer of material.

The inner core and outer layer of material are readily bonded to oneanother. The overall filling material has high rigidity and strength dueto the presence of the inner core in combination with the low meltingand good fusion character of the outer layer of material, making itcapable of effectively bonding to a sealant.

In yet another embodiment herein, the filling material having the coresection and outer layer section is fabricated in the form of dentalappliances including dental obturators or endodontic posts. In anobturator, the core section forms the shaft of the obturator and theouter layer section forms the filling material on the obturator. In anendodontic post, the core section forms the post section of the post andthe outer layer section forms the filling tip section of the post.

BRIEF DESCRIPTION OF THE DRAWINGS

Features of the present invention are disclosed in the accompanyingdrawings, wherein similar reference characters denote similar elementsthroughout the several views, and wherein:

FIG. 1 is a graph showing bacterial leakage of test samples after 30days;

FIG. 2 is a graph showing bacterial leakage of test samples after 30days;

FIG. 3 is an elevational view of a sample placed in an Instron machinefor fracture testing;

FIG. 4 is an elevational view of the sample shown in FIG. 3;

FIG. 5 is an elevational view of an appliance having a filling materialthereon;

FIG. 6 is an elevational view of a post as an alternate carrier inaccordance with the invention;

FIG. 7 is an elevational view of an alternate embodiment of an alternatecarrier in accordance with the invention;

FIG. 8 is an elevational view of yet another alternative embodiment ofthe invention;

FIG. 9 is an elevational view of an appliance having a filling materialthereon;

FIG. 10 is an elevational view of a post as an alternate carrier inaccordance with the invention;

FIG. 11 is an elevational view of an alternate embodiment of analternate carrier in accordance with the invention; and

FIG. 12 is an elevational view of yet another alternative embodiment ofthe invention.

DESCRIPTION OF THE INVENTION

As will be appreciated, the present invention provides a fillingmaterial for root canals and cavities comprising a thermoplasticpolymer. The thermoplastic polymer may be biodegradable. A bioactivesubstance may be combined with the biodegrable thermoplastic polymer.The thermoplastic polymer acts as a matrix for the bioactive substance.The composition may include other polymeric resins, fillers,plasticizers and other additives typically used in dental fillermaterials including, but not limited to, antibiotic, cariostatic,antibacterial, or other anti-inflammatory, biologically active,therapeutic materials, pigments and dyes. The composition may also beuseful for root canal sealants, implants and pulp capping materials.

It is important that the thermoplastic polymer bonds well to the rootcanal sealant that is applied to the root canal. The bond strength ofthe thermoplastic polymer to the root canal sealant is equal to orgreater than about 3 MPa, and preferably equal to or greater than about4 MPa and most preferably equal to or greater than about 5 MPa.

Suitable thermoplastic polymers for use as the matrix arepharmaceutically compatible. It is preferred that the polymers arebiodegradable by cellular action and/or by the action of body fluids.Examples of appropriate thermoplastic polymers include but are notlimited to polylactides, polyglycolides, polycaprolactones,polyanhydrides, polyamides, polyurethanes, polyesteramides,polyorthoesters, polydioxanones, polyacetals, polyketals,polycarbonates, polyorthocarbonates, polyphosphazenes,polyhydroxybutyrates, polyhydroxyvalerates, polyalkylene oxalates,polyalkylene succinates, polyethylene oxides,polyacrylates/methacrylates, poly(malic acid) polymers, polymaleicanhydrides, poly(methylvinyl) ethers, poly(amino acids), chitin,chitosan, and copolymers, terpolymers, or combinations or mixtures ofthe above materials.

Preferred materials are the polylactides, polyglycolides,polycaprolactones, and copolymers thereof. These polymers can be used toadvantage in the polymer system in part because they show excellentbiocompatibility. They produce little, if any, tissue irritation,inflammation, necrosis, or toxicity. In the presence of water, thesepolymers produce lactic, glycolic, and hydroxycaproic acid,respectively, which are readily metabolized by the body. Thepolylactides and polycaprolactones can also incorporate glycolidemonomer to enhance the resulting polymer's degradation. Thebiodegradable thermoplastic polymer may be present in an amount fromabout 10 to about 100 percent by weight.

The bioactive material may include any substance or metabolic precursorthereof, which is capable of promoting growth and survival of cells,tissues, and bone. Suitable bone growth promoting substances include butare not limited to bioglass, calcium phosphate, Portland cement,hydroxyapatite, tricalcium phosphate, a di- or polyphosphonic acid, ananti-estrogen, a sodium fluoride preparation, a substance having aphosphate to calcium ratio similar to natural bone, calcium hydroxide,other suitable calcium-containing compounds, and the like. A bone growthpromoting substance may be in the form of a particulate or fiber fillerin nano, micro or macro form, or mixtures thereof, bone chips, bonecrystals or mineral fractions of bone and/or teeth, a synthetichydroxyapatite, or other suitable form. The bioactive filler may bepresent in an amount of up to about 90 percent by weight.

The biodegradable thermoplastic polymers should have meltingtemperatures of about 50 to about 300° C., preferably about 60 to about250° C., and most preferably about 70 to about 200° C. The meltingtemperature of the polymers in these ranges facilitates the process ofcompounding the thermoplastic polymer with bioactive inorganicparticulates and other additives. Furthermore, the melting temperaturerange of the polymers also facilitates the application of the fillingmaterial made from the compounds into a root canal with conventionalaccessible heating methods.

Examples of additional polymeric resins useful in the fillingcomposition or useful in the inner core material or carrier sectioninclude, but are not limited to, polyamides, polyester, polyolefins,polyimides, polyarylates, polyurethanes, vinyl esters or epoxy-basedmaterials, styrenes, styrene acrylonitriles, ABS polymers, polysulfones,polyacetals, polycarbonates, polyphenylenes, polyphenylene sulfides,polyarylsulfides, acrylonitrile-butadiene-styrene copolymers,polyurethane dimethacrylates (hereinafter abbreviated to “UDMA”,triethylene glycol dimethacrylate (hereinafter abbreviated “TEGDMA”),polyethylene glycol dimethacrylate (hereinafter abbreviated “PEGDMA”),urethane dimethacrylate (hereinafter abbreviated “UDMA”), hexane dioldimethacrylate (hereinafter abbreviated “1,6 HDDMA”) and polycarbonatedimethacrylate (hereinafter abbreviated “PCDMA”) and the like. Among theexamples given, the resins containing surface functional groups such asacrylate/methacrylate, epoxy, hydroxyl and others are preferred sincethey not only serve as plasticizers for the compositions but as adhesivecomponents as well for promoting the bonding between the compound and asealant. Preferred polymeric matrix materials include those based onacrylic and methacrylic monomers, for example those disclosed in U.S.Pat. Nos. 3,066,112, 3,179,623, and 3,194,784 to Bowen; U.S. Pat. Nos.3,751,399 and 3,926,906 to Lee et al., and commonly assigned U.S. Pat.No. 5,276,068 to Waknine (which are herein incorporated by reference).An especially preferred methacrylate monomer is the condensation productof bisphenol A and glycidyl methacrylate, 2,2′-bis[4-(3-methacryloxy-2-hydroxy propoxy)-phenyl]-propane (hereinafterabbreviated “BIS-GMA”).

Other fillers which may be used in addition to the bioactive materialinclude inorganic and organic particulates and fibrous fillers known inthe art including, but are not limited to, silica, silicate glass,quartz, zinc oxide, barium sulfate, barium silicate, strontium silicate,barium borosilicate, strontium borosilicate, borosilicate, lithiumsilicate, amorphous silica, bismuth compounds such as BiOCl, Bi₂O₃,ammoniated or deammoniated calcium phosphate and alumina, zirconia, tinoxide, and titania, among other conventional fillers such as thosedisclosed in commonly assigned U.S. Pat. Nos. 4,544,359 and 4,547,531 toWaknine (which are incorporated herein by reference). Some of thefillers also act as radiopaque/high refractive index materials, such asapatites, silica glass fillers, calcium silicate based fillers,hydroxyapatites, barium sulfate, bismuth subcarbonate, ytterbium oxide,ytterbium fluoride, ytterbium iodine, bismuth oxide, bismuth fluoride,barium oxide, and tantalum oxide. Fibrous fillers also include, but arenot limited to, include glass, ceramic, metal, carbon, graphite,polymeric such as cellulose, polyamide, aramid, polyester, polyaramid,acrylic, vinyl and modacrylic, polyolefin, polytetrafluorethylene,mixtures thereof, as well as other fibers known in the art. The fibersmay be of uniform or random length, unidirectional or multidirectional,or randomly dispersed, and may be as short as about 3 to about 4millimeters (mm) or shorter. The fibers may also be in the form offabric as set forth in U.S. Pat. No. 6,186,791, or as possiblereinforcing fibers, as used in U.S. Pat. Nos. 4,717,341 and 4,894,012 toGoldberg et al., all of which are hereby incorporated by reference.

Examples of plasticizers useful in the filling composition include, butare not limited to, polyol, polyolefin or a mixture thereof. Theplasticizer can be incorporated into the composition in the range of upto about 40 percent by weight, preferably up to about 30 percent byweight, and most preferably up to about 20 percent by weight.

In a method for restoring a root canal in accordance herein, the rootcanal is prepared by the dentist. This can involve inserting endodonticfiles or reamers into the canal to remove pulp, necrotic tissue, organicdebris, and other potential irritants. Thereafter, an etchant is appliedto the root canal wall. Examples of etchants include, but are notlimited to, organic acids or their derivatives such as an ethylenediamine tetra acetic acid (EDTA) solution, amino acid, acrylic acid,maleic acid, citric acid, tartaric acid, itaconic acid, 5-sulfosalicylicacid, propionic acid, lactic acid and the like; inorganic acids such asphosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, and thelike. Useful etchants for the process herein disclosed are described incommonly assigned U.S. Pat. No. 6,537,563, which is hereby incorporatedby reference.

In general, the commercial dental etchants used for dentin surfaceconditioning/etching are all suitable for root canal etching purposes.Commercially available etching gels suitable for this purpose areavailable from Pentron Clinical Technologies, LLC as 10% phosphoric acidetching gel and 37% phosphoric acid etching gel. Preferably, the etchantis a self-etch bonding agent such as described in commonly owned,copending U.S. Application No. 20020019456, which is hereby incorporatedby reference. A commercially available self-etch primer useful herein isNanoBond™ self-etch primer from Pentron Clinical Technologies, LLC.Other examples of commercially available self-etch primer/adhesives areSE Bond™ available from Kuraray, Prompt L-Pop™ available from 3M/ESPEcompany, and iBond™ available from Kulzer. The resin modified glassionomer based sealants can also be used in conjunction with the rootcanal filling material.

Alternatively, if the etchant does not include an adhesive, a bondingagent may further be applied to the walls of the root canal. Examples ofbonding materials include, but are not limited to, dentalacrylate/methacrylate based resin adhesives. Commercially availablebonding agents include, but are not limited to, Bond-It® and Bond-1®bonding agents available from Pentron Clinical Technologies, LLC, AllBond 2™ and One Step™ available from Bisco, Prime & Bond™ available fromDentsply, ScotchBond™ available from 3M, and PermaQuik™ available fromUltradent. Thereafter, a sealant is applied into the root canal.Examples of sealants include, but are not limited to,acrylate/methacrylate resin based root canal sealants, epoxy resin basedsealants, and the like and the sealants disclosed in commonly assignedU.S. Pat. No. 6,455,608, which is hereby incorporated by reference.Commercially available sealants include FiberFill™ root canal sealantavailable from Pentron, AH-26™ available from LD Caulk/Dentsply andEndoRez™ available from Ultradent. After the sealant is applied, thefilling material is inserted into the canal. It may applied in a varietyof ways including, but not limited to, lateral condensation, verticalcondensation of soft material, and single points of material eitherinserted individually or applied to a carrier and inserted into thecanal via the carrier. The canal is then filled with a filling materialthat may or may not include a post to provide added support for theremaining tooth structure. An artificial crown, direct or indirectrestoration, fixed-partial denture abutment, etc. can then be placedover the tooth to complete the tooth restoration.

Alternately, one-step adhesives or sealants may used such as EndoRez™available from Ultradent or Epiphany™ SE sealant available from PentronClinical Technologies, LLC in place of the previous-discussed methods asa single step to replace etching, priming and/or bonding. Thereafter,the filling material or obturator is inserted.

The materials and process described herein provide superior sealing andfilling of the root canal. The materials used to seal and fill the rootcanal form a monoblock of material that is bonded to the wall of theroot canal to reduce or eliminate leakage of bacteria into the canal.Moreover, the filling materials described herein are easily removablefrom the root canal. One example of removing the filling material fromthe root is by dissolving the material in a solvent such as acetone,chloroform or other chlorinated hydrocarbons, aromatic hydrocarbons,tetrahydrofuran, limonene, eucalyptus oil, xylene, benzene, toluene or amixture thereof.

Leakage tests were performed over a thirty day period on samples ofteeth using various forms of filling materials. A split chambermicrobial leakage model was used wherein S. mutans or S. faecalis (seegroups below), which were placed in the upper chamber, could reach thelower chamber only through the obturated canal. A lower chamberconsisted of 15 ml of Basal Broth with Phenol Red indicator to which 1%sucrose was added. The specimens were checked every 24 hours over aperiod of 30 days for a change in the color of the broth or of the pHindicator from red to yellow (metabolism as acid production), whichindicated bacterial leakage. The average rate of leakage of bacteria wascompared between all groups over 30 days by usingCochran-Mantel-Haenszel row means score statistics. Leakage was assessedevery day for 30 days. The groups tested were as follows. Group 1consisted of ten teeth that were filled with gutta-percha, but withoutthe use of a sealer (Positive Control). Group 2 consisted of ten teethprepared as in Group 1, but the entire system was sealed to test itsability to stop bacteria from moving through it (Negative Control).Group 3 consisted of fifteen teeth having AH26 sealant applied and thenfilled laterally with gutta-percha and condensed (LT-AH26). Group 4consisted of fifteen teeth having AH26 sealant applied and then filledvertically with gutta-percha and condensed (VT-AH26). Group 5 consistedof fifteen teeth having AH26 sealant applied and then filled with Obturasoft gutta-percha (Obtura-AH26). Group 6 consisted of fifteen teethprepared and etched with a self etching primer, followed by applicationof a root canal sealant, followed by the lateral insertion of resinmaterial (resin percha) in accordance with the invention (LT ResinPercha). Group 7 consisted of fifteen teeth prepared and etched with aself etching primer, followed by application of a root canal sealant,followed by the vertical insertion of resin material (resin percha) inaccordance with the invention (VT Resin Percha). Groups 8 and 9 wereidentical to Groups 6 and 7, respectively, except that unlike Groups 1to 7 that used S. mutans bacteria, Groups 8 and 9 used S. faecalisbacteria. The results are shown in Table 1 below.

TABLE 1 NUMBER OF LEAKAGE OF TEETH AFTER NUMBER OF DAYS GROUP TEETH 1day 3 days 6 days 9 days 12 days 15 days 18 days 21 days 24 days 27 days30 days 1 10 10 10 10 10 10 10 10 10 10 10 10 Positive Control 2 10 0 00 0 0 0 0 0 0 0 0 Negative Control 3 15 0 0 6 10 12 13 13 13 13 13 13LT-AH26 4 15 0 0 4 8 10 10 10 11 11 11 11 VT-AH26 5 15 0 0 8 10 14 14 1414 14 14 14 Obtura AH26 6 15 0 0 0 0 1 1 1 1 2 2 2 LT Resin Percha 7 150 0 0 0 1 1 2 2 2 2 2 VT Resin Percha 8 15 0 1 1 1 1 1 2 2 2 2 2 LTResin Percha 9 15 0 0 1 1 1 1 1 1 1 1 1 VT Resin Percha

As shown in Table 1, the materials of the invention used in Examples6-9, show leakage in only 1 or 2 of 15 teeth in a period of 30 dayscompared with conventional materials used in Examples 3 through 5, whichshowed leakage of most of the teeth over the same time period.

FIGS. 1 and 2 are graphs showing in-vitro leakage for strep. mutans andEnterococcus. faecalis, respectively, for test groups of 15 teeth usingthe test described above. In FIG. 1, PC, NC, L-GP, V-GP, L-RP and V-RPrefer to positive control, negative control, lateral-gutta-percha,vertical-gutta-percha, lateral-resin percha and vertical-resin percha,respectively. The resin percha used herein comprises Composition C asset forth in Table 3 below. Consistent with Table 1 above, the graph inFIG. 1 shows the positive control tooth having filling material withouta cement (PC) having leakage in all 15 teeth. The negative control,which is a normal tooth, showed no leakage after 30 days. Thegutta-percha inserted both laterally and vertically, show high leakagerates of 13 and 14 teeth, respectively, after 30 days. The resin perchaof the invention showed very low leakage of only 2 teeth after 30 days.

The graph in FIG. 2 representing leakage of Enterococcus. faecalis intest groups of 15 teeth is also consistent with Table 1 and FIG. 1. Asexpected, the positive control shows leakage of all 15 teeth and thenegative control shows no leakage. The laterally placed and verticallyplaced resin percha show low leakage of only 2 teeth and 1 tooth,respectively.

The following examples illustrate the invention.

EXAMPLE 1

Extracted central incisor teeth were prepared with root canal files tostandard sizes so that the remaining walls of the teeth were of asimilar size. The roots were restored as follows Group 1 (15teeth)—positive control—no root canal filling placed. Group 2 (15teeth)—root canals filled with lateral condensation gutta-percha andAH26 sealer. Group 3 (15 teeth)—root canals filled with verticalcondensation gutta-percha and AH26 root canal sealer. Group 4 (15teeth)—root canals walls were prepared with the self etch primer, filledwith root canal sealant sealer and then filled vertically with resinpercha in accordance with the invention. All roots were placed in acontainer with 100% humidity for 2 weeks until the strength tests wereperformed. After two weeks the teeth were mounted into a plastic ringwith commercial resin to a level that left 8 mm of root above the resin.The rings were mounted into an Instron machine in which a ballattachment was placed so as to create a wedge-like force along the longaxis of the tooth when activated. Reference is hereby made to FIGS. 3and 4, which show the placement of the samples in the Instron machine.When the correct position of the ball on the tooth was confirmed, theInstron machine was activated so that a slowly increasing force wasapplied to the root until fracture occurred. The resistance to fracture(fracture force) for each tooth in each group was recorded and the meanfracture values for the groups are compared in Table 2 below.

TABLE 2 Group 1 - Control 360 lbs Group 2 - 331 lbs GP Lateral Group 3 -380 lbs GP Vertical Group 4 - 460 lbs RP vertical

As can be seen from the results in Table 2, the groups in whichgutta-percha was used (Groups 2 and 3) were no different from thecontrol group (Group 1) having no root canal filling. The resin perchagroup (Group 4) showed a 22% increase in strength over the control(Group 1).

EXAMPLE 2

A composition comprising polycaprolactone available from Union Carbidein an amount of about 40%, a bioactive glass having a compositionsimilar to Bioglass™ (available from by U.S. Biomaterials) in an amountof about 30%, USP grade zinc oxide in an amount of about 20% and bariumsulfate as a radio-opacifying agent in an amount of about 10% wasmanufactured. The method of forming the composition involved heating thepolycaprolactone at about 70° C. to a softened state. The remainingingredients were then added and mixed under the action of kneading,pressing, or mixing to blend into the polycaprolactone completely toform a homogenous dough. The formed compound was then ready forapplication to the carrier device.

EXAMPLE 3

A composition comprising polycaprolactone in an amount of about 30%,caprolactone (methacryloxy)ethyl ester (CMEE) in an amount of about 10%,tricalcium phosphate in an amount of about 30%, and zirconium oxide inan amount of about 10% was manufactured. The method of forming thecomposition involved heating the polycaprolactone (available from UnionCarbide) at about 70° C. to a softened state. The remaining ingredientswere then added and mixed under the action of kneading, pressing, ormixing to blend into the polycaprolactone completely to form ahomogenous dough. The formed compound was then ready for application tothe carrier device.

The following Table 3 sets forth examples of the filling materialcompositions made similar to the methods described in Examples 2 and 3above.

TABLE 3 Composition WEIGHT (%) A B C D E P767* 40 30 21 25 P787* 9 27PEGDMA(400) 5 8 UDMA 10 CMEE** 10 Bioactive glass 30 10 21.5 30 ZnO 2010 21.5 25 25 BaSO₄ 20 22 20 BiOCl 10 Ca(OH)₂ 20 Ca₃(PO₄)₂ 20 ZrO₂ 10*P767 and P787 are polycaprolactone resins sold under the trade name ofTONE ™ POLYMER by Dow Chemical Co. **CMEE is caprolactone (methacryloxy)ethyl ester

The compositions were then prepared for bonding strength tests asfollows:

Sample Preparation for Bonding Tests

The compositions from Table 3 above were softened at about 80° C. in aconvection oven. While the materials were at a workable consistency,they were placed in 15 mm diameter and 1.2 mm thickness steel moldsbetween two glass slides and were cooled down to bench temperature.Sample disks were formed and the glass slides and molds were removed.Some trimming was necessary to remove the flashes from the edge. Fivediscs were prepared for each test material.

The sample disks were then mounted into a cold-cured acrylic mountingmaterial in a splitable cylindrical TEFLON™ mold of a 20 mm diameter andabout a 30 mm height, leaving one side of the disk exposed. Atwo-component self curable A2 shaded Cement-It™ C&B Universal Cement(Pentron Corp., Wallingford, Conn.), which is a methacrylate resincement, was used to make a composite button and was bonded directly tothe exposed sample surfaces. Number five (#5) Gelatin capsules (TorpacInc. NJ) were used to load the cement and were placed directly onto thesurfaces under a load of 500 grams on a Bencor testing device (DenvilleEngineering, CA) until the cement hardened. The cement has a settingtime of approximately 4 minutes after the two components are mixed.After one hour of bench setting, the bonded samples were debonded with apush shear mold in a Bencor test device under a crosshead speed of 0.02in/minute. The maximum load at which the cement cylinders broke from thesample surfaces was recorded. Bonding strengths were calculated usingthe load divided by the contact surface area of the cement cylinder.

The following Table 4 sets forth bonding strengths of the fillingcompositions in Table 3 along with a gutta-percha composition forcomparison.

TABLE 4 Compositions Bond Strength, MPa (S.D.) A 3.2 (1.1) B 5.5 (2.3) C6.5 (1.9) D 6.8 (0.7) E 6.8 (1.2) Gutta-percha Control* 0 (Samples allfailed before testing) *The control is a dental gutta-percha materialavailable from Endodent, Inc. Duart, CA

Transverse Deflection Tests

To test the flexibility of the compositions herein, a testing apparatusfor the transverse deflection test as described in ADA specificationNumber 12 for Denture Base Polymers was adopted for the test. The testsamples were made into bars of 50×3×3 mm in a TEFLON splitable moldwhile the materials were at a soft stage. A 500 gram weight was appliedonto the center of the test sample through the loading nose. The spanbetween the two supports was 30 mm. The still load was removed after oneminute (if the sample had not broken during the standing period) and themaximum deflection distance was measured and recorded. Three testsamples were run for each test material. The test results are shown inTable 5.

TABLE 5 Maximum Deflection Time of Test Samples Compositions Distance(mm) withstanding the load) A 6-8 Full minute without break C 7-9 Fullminute without break Gutta-percha 1-3 1-2 seconds (Broke almost Controlinstantly after applied the load)

The results of the inventive materials are shown to have superiorresults over the gutta-percha material.

The bioactive material can be miscible in the polymer to provide ahomogeneous mixture with the polymer, or insoluble in the polymer toform a suspension or dispersion with the polymer. The filling materialmay be in the form of a cone to be inserted into a canal. The cone maybe inserted into the canal using a file or similar instrument, or it maybe attached to a file, shaft or similar carrier which instrument is theninserted into the canal with the cone thereon. After insertion, thecarrier is removed or the excess of the cone is cut off as in aconventional gutta-percha cone application from the root canal.

Alternatively, the material may be softened and compacted toward theapex, while it is still in the softened state, to ensure the apex isadequately sealed. This may be done by a backfilling technique whereby,for example, the material is heated and injected into the canal using adevice having a needle, such as the Obtura II device available fromObtura/Spartan, Fenton, Mo.

If, by chance, the filling material is pushed slightly past the apex, orseeps through the apex, or comes in contact with fluids in the mouth,the biodegradable material will disintegrate or break down and beabsorbed or partially absorbed by the surrounding living tissues and thebioactive substance present in the filling material will react withtissue in the mouth, mending and/or growing tissue to fill any gaps oropenings.

Commonly assigned U.S. Pat. No. 6,455,608 is directed to dentalcompositions comprising degradable polymers for use as root canalsealants, implants and pulp capping materials and is hereby incorporatedby reference. The compositions use polymerizable and degradablemacromonomers to provide precursors for forming biodegradable andbiocompatible polymers upon a chemical reaction, which advantageouslyallow for tissue regrowth.

As yet another alternative, the filling material may be integrallyformed on a post whereby a single post unit comprises a combinedendodontic post and tip of filling material. To use the post unit, thetip of the device is softened by placing in an oven or heater to heatand soften the filling material or chemically treating to soften thematerial. The device will then be placed in a root canal that has beenopened to a predetermined dimension by use of endodontic files, to sealthe apical end. If necessary, the filling material can be compactedtoward the apex, while it is still in the softened state, to ensure theapex is adequately sealed. The post may then be cemented into place bylining the canal walls with a bonding agent and filling the interfacebetween the post and the walls of the canal with a resin cement such asa dual cure cement, a light cure cement or a self cure cement such asFiberFill™ RCS root canal sealant or Cement-It® Universal cement, bothavailable from Pentron Clinical Technologies, LLC in Wallingford, Conn.This will result in a coronal seal of the canal via a resin restorativematerial and an apical seal of the canal by means of a filling materialand sealant. The remaining portion of the post, extendingsupra-gingivally, will be used to build a core around it. Any excesswill be cut off. One length of the device will be longer to accommodatethe longer roots in anterior teeth. Another length will be shorter toaccommodate smaller roots in the molar region. Various diameters mayalso be provided to accommodate the different sizes of root canals. Thebonded flexible post may strengthen the tooth to prevent subsequent rootfractures.

Reference is made to FIGS. 5 through 8 which show carriers having thefilling material applied to the tip of the carrier. FIG. 5 shows anappliance 10 having a handle 12 and an elongated shaft 14. Shaft 14 hasa proximal end 14 p and a distal end 14 d that fits in a root canal. Asliding support 16 is positioned between shaft 14 and handle 12 to serveas an indicator of the depth of the canal and to help maintain thecarrier in place. After the appliance is inserted in the canal, slidingsupport 16 is moved to the point at the top of the canal. Fillingmaterial 18, containing a biodegradable thermoplastic polymer and abioactive filler, is positioned on the shaft, starting at the proximalend and continuing down, over the distal end. Reference is hereby madeto commonly assigned U.S. Pat. Nos. 6,447,297 and 6,428,319, andcommonly assigned U.S. patent application Ser. No. 10/164,512 filed Jun.6, 2002, each directed to posts or obturators having filling materialsintegrally formed thereon, and all of which are hereby incorporated byreference.

Turning to FIG. 6, a post unit 20 is shown comprising a post section 21and a cone or tip section 24. Tip section 24 comprises a flexible rod orcone comprising a biodegrable thermoplastic polymer in combination witha bioactive substance for filling the apex of the canal. The fillingmaterial may include additives typical in the dental field such asplasticizing, antibiotic, cariostatic, antibacterial, or otheranti-inflammatory, biologically active or therapeutic materials.

Post section 21 comprises a main body or endodontic portion 22 and acarrier or apical portion 23, which is located at the apical end of postunit 20. Main body 22 may be a solid rod of circular or other suitablecross-section comprising a substantially smooth surface or may comprisea plurality of frustoconical sections arranged coaxially along thelongitudinal axis of main body 22. Preferably, main body 22 hasconsistent width along the longitudinal axis thereof whereasfrustoconical sections each have the same tapered width and same length.It is possible to vary the width and/or length of main body 22 and/orvary the tapered width and/or length of frustoconical sections along thelongitudinal axis of main body 22.

Carrier 23 is preferably an extension of main body 22 of post section 21and is of very fine diameter to accommodate tip section 24 ofthermoplastic material of post unit 20. In one method of manufacturewhich will be discussed hereinafter, post section 21 is manufacturedfrom a rod of material that is cut or machined at the apical end toresult in carrier 23 having a very small width or diameter in comparisonto main body 22. Carrier 23 is of small diameter to allow enough area toform tip section 24 thereon, and also of enough strength and integrityto accommodate the filling material as discussed above. As stated above,carrier 23 is preferably an extension of main body 22 and is shownhaving constant diameter along the length thereof, but may be of anyshape or size sufficient to hold tip section 24 thereon.

Post section 21 may be fabricated of any material to provide a flexibleapical portion and a more rigid endodontic and/or coronal orsupracoronal portion, such as metal, plastic, ceramic, polymeric,composite, or other material suitable for placement in the mouth.Composite materials include but are not limited to filler reinforcedcomposite materials and fiber reinforced composite materials comprisingthe reinforcing component in a polymeric matrix material such as thosecomposite materials listed in U.S. Pat. Nos. 4,717,341 and 4,894,012 toGoldberg et al., U.S. Pat. No. 6,039,569 to Prasad et al., U.S. Pat. No.6,030,220 to Karmaker et al, U.S. Pat. No. 5,564,929 to Alpert, and U.S.Pat. No. 5,919,044 to Sicurelli, Jr. et al., all of which are herebyincorporated by reference. The fiber reinforced composite material maycomprise fibers in the form of long, unidirectional, continuousfilaments which are preferably at least partially aligned and orientedalong the longitudinal dimension of the component with alignment normalor perpendicular to that dimension also possible. The fibers may be ofuniform or random length, unidirectional or multidirectional, orrandomly dispersed, and may be as short as about 3 to about 4millimeters (mm) or shorter. The fibers may also be in the form offabric as set forth in copending Ser. No. 09/280,760 filed Mar. 29,1999, now U.S. Pat. No. 6,186,791, and may include any of the attributesof the post described therein, the contents all of which are herebyincorporated by reference. Due to the improved structural integrity, theamount of fibers in the structural component preferably equals at leastabout 20% by weight (wt %) and preferably about 20 wt % to about 70 wt%. Possible reinforcing fibers, which are preferably used in accordancewith U.S. Pat. Nos. 4,717,341 and 4,894,012 to Goldberg et al. (whichare herein incorporated by reference), include glass, ceramic, metal,carbon, graphite, polymeric such as cellulose, polyamide, aramid,polyester, polyaramid, acrylic, vinyl and modacrylic, polyolefin,polytetrafluorethylene, mixtures thereof, as well as other fibers knownin the art. One preferred version of the device is comprised ofunidirectional microfilamentous glass fibers bundled in a resin matrix.

In order to enhance the bond between the fibers and polymeric matrix,thereby enhancing the reinforcing effect, the fibers may be silanized orotherwise treated such as by grafting functional monomers to obtainproper coupling between the fibers and the resin matrix. Silanizationrenders the fibers hydrophobic, reducing the water sorption andimproving the hydrolytic stability of the composite material, rendersthe fibers organophilic, improving wetting and mixing, and bonds thefibers to the polymeric matrix. Typical silane is A-174 (p-methacrylatepropyl tri-methoxy silane), produced by OSI Specialties, New York. Thepolymeric matrix is selected from those known in the art of dentalmaterials, including, but not limited to, polyamides, polyester,polyolefins, polyimides, polyarylates, polyurethanes, vinyl esters orepoxy-based materials, styrenes, styrene acrylonitriles, ABS polymers,polysulfones, polyacetals, polycarbonates, polyphenylene sulfides,polyarylsulfides, acrylonitrile-butadiene-styrene copolymers,polyurethane dimethacrylates (hereinafter abbreviated to PUDMA), and thelike. Preferred polymeric matrix materials include those based onacrylic and methacrylic monomers, for example those disclosed in U.S.Pat. Nos. 3,066,112, 3,179,623, and 3,194,784 to Bowen; U.S. Pat. Nos.3,751,399 and 3,926,906 to Lee et al.; and commonly assigned U.S. Pat.No. 5,276,068 to Waknine (which are herein incorporated by reference).An especially preferred methacrylate monomer is the condensation productof bisphenol A and glycidyl methacrylate, 2,2′-bis[4-(3-methacryloxy-2-hydroxy propoxy)-phenyl]-propane (hereinafterabbreviated “BIS-GMA”). The polymer matrix, which typically includespolymerization initiators, polymerization accelerators, ultra-violetlight absorbers, anti-oxidants, fluorescent whitening agents, freeradical initiators, and/or other additives well known in the art, may bevisible light curable, self-curing, dual curing, or vacuum, heat, orpressure curable compositions, as well as any combination thereof. Heatand pressure or vacuum curable compositions include a heat cureinitiator such as benzoyl peroxide,1,1′-azobis(cyclohexanecarbo-nitrile) or other free radical initiators.The preferred polymeric matrix is a light and heat curable matrix,wherein light effects partial cure of the polymer matrix, while finalcuring is by heat under controlled atmosphere.

Fillers may be present in addition to or instead of fibers in an amountup to about 80 wt %, and preferably about 70 wt %. If fibers arepresent, the amount of filler is present in an amount of up to about 30wt % of one or more fillers known in the art and used in dentalrestorative materials. Suitable fillers include those capable of beingcovalently bonded to the polymeric matrix itself or to a coupling agentthat is covalently bonded to both. Fillers include silica, silicateglass, quartz, barium silicate, strontium silicate, barium borosilicate,strontium borosilicate, borosilicate, lithium silicate, amorphoussilica, ammoniated or deammoniated calcium phosphate and alumina,zirconia, tin oxide, and titania, among other conventional fillers suchas those disclosed in commonly assigned U.S. Pat. Nos. 4,544,359 and4,547,531 to Waknine (which are incorporated herein by reference), whilepossible coupling agents include silanes, zirconates, and titanates. Ifthe post is manufactured from a composite material, it is preferably incompletely cured or hardened state.

Examples of metals useful as post section 21 include but are not limitedto metals or alloys of Pd, Pt, Rh, Ir, Au, Ag, Ti, Co, Mo and mixturesthereof such as AgPd, AuPtPd, TiAlFe, TiAlV, CoCrMo, stainless steel andbrass. Ceramic materials useful in the fabrication of post section 21include but are not limited to alumina, zirconia, mullite, spinel,porcelain, titania, lithium disilicate, leucite, amorphous glass,lithium phosphate, and combinations thereof, or any high strengthceramic material which can withstand the stresses created in the mouth.

Carrier 23 preferably comprises a smooth surface, although it is in noway limited to such and may be of any surface suitable for applicationof filling material thereon. The post may be provided in an opaque toothcolor or it may be colored similar to a tooth's pulp for enhancedesthetics. The post may include an appropriate amount of radiopaquematerial such as titanium oxide, barium sulfate, and similar materialsknown in the dental industry to insure x-ray documentation which may beadded to the post material during manufacture thereof. After postsection 21 has been manufactured, carrier 23 of post section 21 is thencoated with a filling material such as set forth above to obtain conesection 24 thereon. The filling material may be applied by any knownmeans such as dipping, injection molding, hand rolling, and the like.

To use the post unit, the device may be used as is, or may be heated byplacing in or near an oven or heater to heat and soften the fillingmaterial or dipped in a chemical solution such as chloroform to softenthe filling material. The device will then be placed in a root canalthat has been opened to a predetermined dimension by use of endodonticfiles, to seal the apical end. If necessary, the filling material can becompacted toward the apex, while it is still in the softened state, toensure the apex is adequately sealed. The post is then cemented intoplace by lining the canal walls with a bonding agent and filling theinterface between the post and the walls of the canal with a resincement, such as a dual cure cement. This will result in a coronal sealof the canal via resin restorative material and an apical seal of thecanal by means of filling material and sealant. The remaining portion ofthe post, extending supra-gingivally, will be used to build a corearound it, and if necessary, for placement of a crown thereon. Anyexcess of the post will be cut off. One length of the device will belonger to accommodate the longer roots in anterior teeth. Another lengthwill be shorter to accommodate smaller roots in the molar region.

FIG. 7 shows a post unit 30 that comprises a post section 32 fabricatedof fiber reinforced composite material. Post section 32 includes mainbody 34 and carrier 36. Carrier 36 is coated with a filling material toobtain cone section 38 thereon. As shown in the drawing, main body 34 istapered to provide ease of placement into the canal. The cross-sectionof post unit 30 may be smaller than the cross-section of a standard postto fit in thinner or smaller auxiliary canals which are normally filledwith a thermoplastic material. Accordingly, post unit 30 can act as anobturator. As an obturator, better support is provided due to thefiber-reinforced composite structural component 34 upon which conesection 38 is applied in comparison to using only a thermoplasticmaterial as an obturator. Moreover, the obturator may be easily cementedin place in the canal. Post unit 30 may also include a handle 40 whichis beneficial when the post unit is used as an obturator. Handle 40 maybe any filled or unfilled polymeric material, such as those mentionedabove and used in the fabrication of the post.

FIG. 8 is directed to an obturator 40 having filling core or point 42and a handle 44. Filling core 42 is a shaft 46 having a proximal end 46p and a distal end 46 d that fits in a root canal. A sliding support 48is positioned between shaft 46 and handle 44 to serve as an indicator ofthe depth of the canal and to help maintain the obturator in place.After the appliance is inserted in the canal, sliding support 48 ismoved to the point at the top of the canal. Obturator 40 is cut off atthe point desired to fit the canal. Filling core 42 containing abiodegrable thermoplastic polymer and optionally, a bioactive filler, inthe form of shaft 46, fills the canal. The filling core 42 and handle 44are a single unit fabricated of a biodegradable thermoplastic polymerand optionally, a bioactive filler. Alternatively, the filling core ismade of a biodegradable thermoplastic polymer and optionally, abioactive filler and the handle may be fabricated of any know materialincluding but not limited to metal, plastic, composite, ceramic, glassor polymeric material.

The compositions of the inventive materials have a radiopacity similarto gutta-percha materials.

FIG. 9 shows an alternate embodiment herein showing a cone 90 fabricatedof filling material. Cone 90 includes an inner core section 92 and anouter layer of material 94 disposed on and surrounding inner coresection 92. Inner core section 92 and outer layer of material 94 eachare fabricated of a thermoplastic polymer matrix material. Thethermoplastic polymer matrix material used in both inner core section 92and outer layer of material 94 may be the same polymer or a differentpolymer, but the melt flow index and the molecular weight will bedifferent. The melting points of the polymer matrix materials may be thesame, in the range of about 50 to about 300° C., preferably about 60 toabout 250° C., more preferably about 70 to about 200° C. and mostpreferably in the range of about 60 to about 100° C.

The thermoplastic polymer matrix material in inner core section 92 has alower melt flow index than the melt flow index of the thermoplasticpolymer matrix material in outer layer of material 94. It is preferablethat the melt flow index of the thermoplastic polymer matrix material ininner core section 92 is in the range of about 0.1 to about 4.0 gramsper minute, and more preferably in the range of about 0.5 to about 3.0grams per minute at 80° C. and/or 44 psi. It is preferable that the meltflow index of the thermoplastic polymer matrix material in outer layerof material 94 is in the range of about 4.5 to about 20.0 grams perminute, and more preferably in the range of about 5.0 to about 15.0grams per minute at 80° C. and/or 44 psi.

The variations in the melt flow indices of the thermoplastic polymermatrix materials allow for softening of outer layer of material 94 whenheated to allow for slight shaping or modification to the contours ofthe root canal and for ease of placement therein. At the same time,inner core section 92 maintains rigidity and integrity as cone 90 isforced into the root canal. The use of the same or similar thermoplasticpolymer matrix materials promotes good bonding between inner coresection 92 and outer layer of material 94

The thermoplastic polymer matrix materials may be any of those listedabove in the description, which provide strong adherence to the rootcanal sealant used in the endodontic process. The thermoplastic polymermatrix preferably has little or no gutta percha or polyisoprene present,which presence could decrease bonding at the sealant/filling materialboundary. It is preferable that the thermoplastic polymer matrixmaterials are gutta-percha-free or polyisoprene-free. The thermoplasticpolymer matrix materials may also include other additives as mentionedabove such as fillers, plasticizers, adhesives, additional resins,additional fillers, pigments, dyes, antibiotics, cariostatics,antibacterials, anti-inflammatories, biologically active materials, andtherapeutic material.

Cone 90 may be inserted into the root canal by any know means including,but not limited to, using a file or similar instrument, or attaching toa file, shaft or similar carrier which instrument is then inserted intothe canal with the cone thereon. After insertion, the carrier is removedor the excess of the cone is cut off as in a conventional gutta-perchacone application from the root canal. Alternatively, the material may besoftened and compacted toward the apex, while it is still in thesoftened state, to ensure the apex is adequately sealed. This may bedone by a backfilling technique whereby, for example, the material isheated and injected into the canal using a device having a needle.

In an alternate embodiment herein, filling material is provided in theform of an appliance. FIGS. 10 and 11 show appliances 100 and 110,respectively. Appliances 100 and 110 have shafts 101 and 111,respectively, which have bonded thereto filling material 102 and 112,respectively. Shafts 101 and 111 and filling material 102 and 112 arefabricated of a thermoplastic polymer matrix material. The thermoplasticpolymer matrix material used in shafts 101 and 111 and filling material102 and 112 may be the same polymer or a different polymer, but the meltflow index and the molecular weight will be different. The meltingpoints of the polymer matrix materials may be the same, in the range ofabout 50 to about 300° C., preferably about 60 to about 250° C., morepreferably about 70 to about 200° C. and most preferably in the range ofabout 60 to about 100° C.

The thermoplastic polymer matrix material in shafts 101 and 111 has alower melt flow index than the melt flow index of the thermoplasticpolymer matrix material in filling material 102 and 112. It ispreferable that the melt flow index of the thermoplastic polymer matrixmaterial in shafts 101 and 111 is in the range of about 0.1 to about 4.0grams per minute, and more preferably in the range of about 0.5 to about3.0 grams per minute at 80° C. and/or 44 psi. It is preferable that themelt flow index of the thermoplastic polymer matrix material in fillingmaterial 102 and 112 is in the range of about 4.5 to about 20.0 gramsper minute, and more preferably in the range of about 5.0 to about 15.0grams per minute at 80° C. and/or 44 psi.

The variations in the melt flow indices of the thermoplastic polymermatrix materials allow for softening of filling material 102 and 112when heated to allow for slight shaping or modification to the contoursof the root canal and for ease of placement therein. At the same time,shafts 100 and 110 maintain rigidity and integrity as filling material102 and 112 is forced into the root canal. The use of the same orsimilar thermoplastic polymer matrix materials promotes good bondingbetween shafts 100 and 110 and filling material 102 and 112,respectively.

The thermoplastic polymer matrix materials may be any of those listedabove in the description, which provide strong adherence to the rootcanal sealant used in the endodontic process. The thermoplastic polymermatrix preferably has little or no gutta percha present, which presencecould decrease bonding at the sealant/filling material boundary. Thethermoplastic polymer matrix materials may also include other additivesas mentioned above such as fillers, plasticizers, adhesives, additionalresins, additional fillers, pigments, dyes, antibiotics, cariostatics,antibacterials, anti-inflammatories, biologically active materials, andtherapeutic material.

It is preferable that the inner core and outer layer materials eachcontain radiopacifying agents. The inner core and outer layer maycontain the same radiopacifying agent or different radiopacifyingagents. The inner core and outer layer may contain the same level ofradiopacity or different levels of radiopacity. It is preferable thatthe inner core and outer layer contain different levels of radiopacityso that one can see that the outer layer has reached the apex in thecanal. It is preferable that the radiopacity differs between the outerlayer and the inner core by a value of 0.5 mm or greater based on analuminum metal thickness as a reference as measured by the InternationalOrganization for Standardization (ISO) standard 4049. It is preferablethat the radiopacity of the inner core section is in the range of about2 to about 3.5 mm based on an aluminum metal thickness as a reference asmeasured by ISO standard 4049 and the radiopacity of the outer layer ofmaterial is in the range of about 4 to about 7 mm based on an aluminummetal thickness as a reference as measured by ISO standard 4049.

Examples of radiopacifying agents include, but are not limited to, oneor more of apatites, silica glass fillers, calcium silicate basedfillers, hydroxyapatites, barium sulfate, bismuth subcarbonate, bismuthoxychloride, ytterbium oxide, ytterbium fluoride, ytterbium iodine,bismuth oxide, bismuth tri-oxide, bismuth fluoride, barium oxide,tantalum oxide, zinc oxide and zirconium oxide.

It is preferable that the inner core material or section comprisepolysulfone. It is preferable that the molecular weight of thepolysulfone is in the range of about 40,000 to about 80,000, and morepreferably less than 56,000. It is preferable that the polysulfone is inthe range of about 40 to about 90 percent by weight and a radiopacifyingagent is in the range from about 10 to about 60 percent by weight. It isalso preferable that the polysulfone has a melt flow in the range ofabout 15 to about 35 g/10 minutes at a temperature of about 340° C.Examples of commercially available polysufones are Udel P-3703, UdelP-3900, Udel P-1700, all available from Solvay Advanced Polymers, LLC,Alpharetta, Ga.

FIG. 11 shows a handle 113 connected to shaft 111 which may befabricated of the same material as shaft 111 or of a different materialsuch as those known in the art for obturator handles.

It is preferable that the outer layer of filling material is bonded tothe inner core section at a bond strength of about 1 MPa or greater andpreferably about 2 MPa or greater, when measured by ASTM D 3165lap-shear test using test bars injection molded with the core sectionmaterial of size 63×3×9 mm and the outer layer of material being hotglued at 150° C. for 10 minutes under a 1 kg load at about 20 mm fromthe end of each test bar whereby the shear strength is conducted at atensile mode with a test speed of 0.5 mm/min and the recorded load atfailure is divided by the overlapped area to calculate the shearstrength.

It is preferable that the outer layer of material on all the devices andposts herein be symmetrically disposed on the inner core material orsection or shaft. The outer layer of material may be overmolded by knowntechniques including dipping or injection molding. The obturator devicemay include a washer, such as an elastomeric washer that can slide alongthe obturator and can be used to measure the depth of the canal intowhich it is to be inserted. This will aid the practitioner in providingan obturator with the correct length for the patient's root canal.

The method of using the device may include inserting a sealant into theroot canal, inserting the obturator into the root canal so that thedistal end at least substantially reaches the root canal apical end; andsevering the part of the obturator that extends above the coronal end ofthe root canal. Moreover, the method may further include inserting asize verifier into the root canal to measure the length of the rootcanal from the root canal apical end, noting the depth of the sizeverifier in the root using depth indicators, withdrawing the sizeverifier from the root canal, and moving a depth indicator located onthe obturator to correspond to the location of the depth indicator onthe size verifier. The obturator may be heated to soften it prior toinsertion into the patient's canal.

The temperature for the heating should be below the melting temperatureof the inner core material but higher than the melting temperature ofthe outer layer of material so that when in use, the core/carrier cancarry the softened outer layer of material into a root canal withoutsignificant device deformation. The preferred heating temperature forthe preferred embodiment is about 100-250° C., and most preferably,about 130-200° C., where the temperature can have an efficient softeningeffect to the outer layer of material with reasonable short timeperiods, from a few seconds to a few minutes in a heating oven such as aDensHeat™ heating unit (Tulsa Dental), a ThermalFil™ oven (TulsaDental), a SoftCore™ oven (CMS Dental), or the like.

As yet a further embodiment, a post may be fabricated of fillingmaterial as described herein. FIG. 12 shows post 120 having a postsection 121 and a cone or tip section 122. Post section 120 comprises amain body or endodontic portion 123 and a carrier or apical portion 124,which is located at the apical end of post unit 120. Main body 123 maybe a solid rod of circular or other suitable cross-section comprising asubstantially smooth surface or may comprise a plurality offrustoconical sections arranged coaxially along the longitudinal axis ofmain body 123. Preferably, main body 123 has consistent width along thelongitudinal axis thereof whereas frustoconical sections each have thesame tapered width and same length. It is possible to vary the widthand/or length of main body 123 and/or vary the tapered width and/orlength of frustoconical sections along the longitudinal axis of mainbody 123.

Carrier 124 is preferably an extension of main body 123 of post section121 and is of very fine diameter to accommodate tip section 122 ofthermoplastic material of post unit 120. Post section 121 may bemanufactured from a rod of material that is cut or machined at theapical end to result in carrier 124 having a very small width ordiameter in comparison to main body 123. Carrier 124 is of smalldiameter to allow enough area to form tip section 122 thereon, and alsoof enough strength and integrity to accommodate the filling material asdiscussed above. As stated above, carrier 124 is preferably an extensionof main body 123 and is shown having constant diameter along the lengththereof, but may be of any shape or size sufficient to hold tip section122 thereon.

Both post section 121 (comprised of main body 123 and carrier 124) andtip section 122 are fabricated of thermoplastic polymeric matrixmaterial. The thermoplastic polymer matrix material used in both postsection 121 and tip section 122 may be the same polymer or a differentpolymer, but the melt flow index and the molecular weight of thepolymers will be different. The melting points of the polymer matrixmaterials may be the same, in the range of about 50 to about 300° C.,preferably about 60 to about 250° C., more preferably about 70 to about200° C. and most preferably in the range of about 60 to about 100° C.

The thermoplastic polymer matrix material in post section 121 has alower melt flow index than the melt flow index of the thermoplasticpolymer matrix material in tip section 122. It is preferable that themelt flow index of the thermoplastic polymer matrix material in postsection 121 is in the range of about 0.1 to about 4.0 grams per minute,and more preferably in the range of about 0.5 to about 3.0 grams perminute at 80° C. and/or 44 psi. It is preferable that the melt flowindex of the thermoplastic polymer matrix material in tip section 122 isin the range of about 4.5 to about 20.0 grams per minute, and morepreferably in the range of about 5.0 to about 15.0 grams per minute at80° C. and/or 44 psi.

The variations in the melt flow indices of the thermoplastic polymermatrix materials allow for softening of tip section 122 when heated toallow for slight shaping or modification to the contours of the rootcanal and for ease of placement therein. At the same time, post section121 maintains rigidity and integrity as it is forced into the rootcanal. The use of the same or similar thermoplastic polymer matrixmaterials promotes good bonding between post section 121 and tip section122.

The thermoplastic polymer matrix materials may be any of those listedabove in the description, which provide strong adherence to the rootcanal sealant used in the endodontic process. The thermoplastic polymermatrix preferably has little or no gutta percha present, which presencecould decrease bonding at the sealant/filling material boundary. Thethermoplastic polymer matrix materials may also include other additivesas mentioned above such as fillers, plasticizers, adhesives, additionalresins, additional fillers, pigments, dyes, antibiotics, cariostatics,antibacterials, anti-inflammatories, biologically active materials, andtherapeutic material.

The following Table 6 provides examples of formulas for the materialshaving the different melt flow indices.

TABLE 6 High fusion compound for Low fusion outer layer of compound forinner the fillings core (Parts per (Parts per Ingredients hundred)hundred) Tone p-737* 20.4 Tone p-757* 10.2 Tone P-767* 10.2 Tone P-787*20.4 UDMA 3.1 3.1 Bioactive glass 11.0 11.0 BaSO₄ 3.3 3.3 BiOCl 52.0 52Bioactive glass 10.2 10.2 Red iron oxide 0.1 0.1 pigments** *TonePolymers are polycaprolactones and Trademarks of the Dow ChemicalCompany. **The pigment is for illustration purpose. The outer layer andthe inner core material can be made into different colors to distinguishthe layers.

The following Table 7 sets forth the properties of the materials havingthe different melt flow indices.

TABLE 7 Melt Flow Molecular Melting Polymer Matrix Index (80° C.,Weight, Number Temperature, Components 44 psi, g/10 min.) Average(approx.) ° F. (° C.) High Fusion 13 32000 140 (60) Polymer: Tone P-737High Fusion 5 43000 140 (60) Polymer: Tone P-757 Low Fusion 1.9 50000140 (60) Polymer: Tone P-767 Low Fusion 0.5 80000 140 (60) Polymer: ToneP-787

The difference in properties between the inner core, shaft or postsection and the outer filling material section provides strength andrigidity to the core, shaft and post section while allowing slightmolding or forming of the outer filling material. Additionally, shouldthe material have to be removed, the inner core, shaft and post sectionand filling material are dissolvable in a root canal solvent as statedabove, making removal effortless and trouble-free.

While various descriptions of the present invention are described above,it should be understood that the various features can be used singly orin any combination thereof. Therefore, this invention is not to belimited to only the specifically preferred embodiments depicted herein.Further, it should be understood that variations and modificationswithin the spirit and scope of the invention may occur to those skilledin the art to which the invention pertains. Accordingly, all expedientmodifications readily attainable by one versed in the art from thedisclosure set forth herein that are within the scope and spirit of thepresent invention are to be included as further embodiments of thepresent invention. The scope of the present invention is accordinglydefined as set forth in the appended claims.

1. A filling material for root canals comprising: an inner core sectioncomprising a first thermoplastic polymer matrix material; an outer layerof material disposed on and surrounding the inner core section; whereinthe outer layer of material comprises a second thermoplastic polymermatrix material; wherein the second thermoplastic polymeric matrixmaterial comprises a biodegradable thermoplastic polymer matrix and anadhesive.
 2. The filling material of claim 1 wherein the secondthermoplastic polymeric matrix material cannot be mixed, kneaded, orpressed at room temperature.
 3. The filling material of claim 1 whereinthe inner core section and the outer layer of material compriseradiopacifying agents to provide radiopacity to the inner core sectionand the outer layer of material.
 4. The filling material of claim 3wherein the inner core section and outer layer of material exhibitdifferent levels of radiopacities.
 5. The filling material of claim 3wherein the radiopacity of the inner core section and the radiopacity ofthe outer layer of material differ by a value of 0.5 mm or greater asmeasured by International Organization for Standardization (ISO)standard
 4049. 6. The filling material of claim 3 wherein theradiopacity of the inner core section is in the range of about 2 toabout 3.5 mm and the radiopacity of the outer layer of material is inthe range of about 4 to about 7 mm as measured by ISO standard
 4049. 7.The filling material of claim 3 wherein the inner core and the outerlayer of material exhibit the same radiopacity.
 8. The filling materialof claim 3 wherein the radiopacifying agents comprise one or more ofapatites, silica glass fillers, calcium silicate based fillers,hydroxyapatites, barium sulfate, bismuth subcarbonate, bismuthoxychloride, ytterbium oxide, ytterbium fluoride, ytterbium iodine,bismuth oxide, bismuth trioxide, bismuth fluoride, barium oxide,tantalum oxide, zinc oxide and zirconium oxide.
 9. The filling materialof claim 1 wherein the first thermoplastic polymeric matrix materialcomprises polyamides, polyester, polyolefins, polyimides, polyarylates,polyurethanes, vinyl esters, epoxy-based materials, styrenes, styreneacrylonitriles, ABS polymers, polysulfones, polyacetals, polycarbonates,polyphenylene sulfides, polyphenylene, polyarylsulfides,acrylonitrile-butadiene-styrene copolymers, polyurethanedimethacrylates, triethylene glycol dimethacrylate, polyethylene glycoldimethacrylate, urethane dimethacrylate, hexane diol dimethacrylate,polycarbonate dimethacrylate or mixtures thereof.
 10. The fillingmaterial of claim 9 wherein the first thermoplastic polymeric matrixmaterial comprises polysulfone having a molecular weight in the rangefrom about 40,000 to about 80,000.
 11. The filling material of claim 10wherein the polysulfone comprises a molecular weight equal to or lessthan about 56,000.
 12. The filling material of claim 1 wherein the firstpolymeric matrix material comprises polysulfone in the range from about40 to about 90 percent by weight and a radiopacifying agent in the rangefrom about 10 to about 60 percent by weight.
 13. The filling material ofclaim 1 wherein the first or second or both the first and secondpolymeric matrix materials further comprise other polymeric resins,fillers, plasticizers, antibiotic, cariostatic, antibacterial,anti-inflammatory, biologically active, therapeutic materials, pigments,dyes and mixtures thereof.
 14. The filling material of claim 9 whereinthe first thermoplastic polymeric matrix material comprises polysulfonehaving a melt flow in the range of about 15 to about 35 g/10 minutes ata temperature of about 340° C.
 15. The filling material of claim 1wherein the outer layer of material is bonded to the inner core sectionat a bond strength of about 1 MPa or greater when measured by ASTM D3165 lap-shear test.
 16. The filling material of claim 1 wherein theinner core section or the outer layer of material, or both the innercore section and the outer layer of material, are dissolvable in a rootcanal solvent.
 17. The filling material of claim 16 wherein the rootcanal solvents comprise acetone, tetrahydrofuran, limonene, eucalyptusoil, chloroform, chlorinated hydrocarbons, aromatic hydrocarbons,xylene, benzene, toluene or a mixture thereof.
 18. The filling materialof claim 1 wherein the outer layer of material is symmetrically disposedon the inner core section.
 19. The filling material for root canals ofclaim 18 wherein the outer layer of material is overmolded onto theinner core by dipping or injection molding.
 20. An obturator comprisingthe filling material of claim 1 wherein the inner core section is ashaft and the outer layer of material is disposed on the shaft.
 21. Theobturator of claim 20 further comprising an elastomeric washer memberhaving an opening therethrough slideably received on the obturator. 22.The filling material of claim 1 wherein the biodegradable thermoplasticpolymer matrix of the second thermoplastic polymeric matrix materialcomprises polylactides, polyglycolides, polycaprolactones,polyanhydrides, polyamides, polyurethanes, polyesteramides,polyorthoesters, polydioxanones, polyacetals, polyketals,polycarbonates, polyorthocarbonates, polyphosphazenes,polyhydroxybutyrates, polyhydroxyvalerates, polyalkylene oxalates,polyethylene oxides, polyacrylates/methacrylates, polyalkylenesuccinates, poly(malic acid) polymers, polymaleic anhydrides,poly(methylvinyl) ethers, poly(amino acids), chitin, chitosan, andcopolymers, terpolymers, or combinations or mixtures thereof.